Environmentalists and coastal researchers say New Jersey’s efforts to establish commercial oyster farms in shallow coastal waters may be jeopardizing a threatened shorebird.

They are asking the state to delay expansion of the Delaware Bay shellfish farming industry until more studies can be done on its impact on the red knot, thousands of which rely on the bay’s beaches as a rest and feeding stop on its annual 10,000-mile journey from South America to the Arctic.

The American Littoral Society and New Jersey Audubon, along with several scientific researchers, tell The Associated Press there is growing evidence that the oyster farms are interfering with red knots during their crucial fattening-up period each spring. They say workers who tend the shellfish farms before and after low tide can scare the birds away, and that sometimes people don’t even need to be there to interfere with the birds; the elevated racks and bags used to grow the oysters can deter birds from landing and feeding.

Their effort sets up a clash between two worthwhile environmental initiatives. One is raising shellfish, which help remove pollutants from the water, and stabilize shorelines against destructive storms. The other is the effort to protect thousands of red knots, whose survival would be in doubt without the southern New Jersey beaches where they gorge themselves on horseshoe crab eggs.

An advisory committee recently sent a report to the state Department of Environmental Protection recommending that expansion of near-shore aquaculture projects not be expanded until further research can be done on potential harm to the red knots. And a study led by a Rutgers University professor found that increased human activity associated with near-shore aquaculture resulted in some shorebirds abandoning affected areas.

“Given the critical role Delaware Bay plays as a terminal migration stopover before knots breed in the Arctic, these warnings demand that we take a strong precautionary approach to aquaculture development in Delaware Bay,” said Tim Dillingham, executive director of the American Littoral Society, a coastal ecology group.

A study last year showed red knots are bothered by human activity, and tend not to return soon to an area from which they have been disturbed. A 2012 study showed that the racks and bags  some only 3 to 4 inches above the sand  interfere with the movement of horseshoe crabs. And a 2009 study found that horseshoe crabs avoid areas covered by underwater shadows.

DEP spokesman Larry Hajna said the agency received the committee’s report in late August and is reviewing it.

Betsy Haskin, who runs a small family oyster plot on the bay, said the status quo “is entirely workable.” She said growers have agreed to restrictions on their operations and movements to minimize any impacts on the birds.

“I don’t think we’re endangering anything,” she said. “We’re a very environmental business. I grew up here; I love these birds and I would never do anything to put myself against them.”

Haskin said there are three aquaculture permits up for renewal soon, all held by small family farmers. She said the real possibility for expansion lies in offshore, deeper water that would have much less of a potential impact on shorebirds.

Michael DeLuca, director of the New Jersey Aquaculture Innovation Center at Rutgers, said the 12 projects currently operated in Delaware Bay waters by private growers were plotted to avoid interfering with red knots as much as possible. He said the farms, spread along about a mile of Delaware Bay shoreline, occupy 1 to 2 percent of the area where horseshoe crabs lay eggs.

“Horseshoe crabs have rebounded somewhat, there has been a restoration of Delaware Bay beaches that were damaged by Superstorm Sandy, and this past spring was a pretty good year for red knots,” he said. “This is an industry that is emerging; it has a $20 million value to the state and can grow tremendously. There needs to be some balance between the protection of the red knots and the economic interests of the state with these projects.”

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Wayne Parry can be reached at http://twitter.com/WayneParryAC

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This story has been corrected to remove a reference to the population of red knots as the world’s largest.